1. Field of the Invention
This invention relates to a closure for a container and more particularly to an improved tamper-proof closure and method of fabricating the closure.
2. Description of the Prior Art
It is desirable to provide a closure body for a container which also visibly indicates unsealing or tampering with the container. This is particularly useful in the area of consumer food products for indicating to the purchaser that the edible contents of the container have not been contaminated or adulterated subsequent to bottling.
A tamper-proof closure body is known which is fabricated of a polymer plastic material and which includes integrally formed cap, ring and frangible bridge members. The cap member is internally threaded for engaging an external thread on a neck of the container; the ring member includes ratchet segments which register with corresponding pawl segments formed on the container; and, the frangible bridge members intercouple the cap and ring members adjacent the ratchet segments and maintain these members in spaced relationship. When this form of tamperproof cap is initially rotated into engagement with the neck of the container, the plurality of ratchets on the resilient ring rotate over and engage the pawls formed on the container neck. A subsequently applied reverse, removal force will encounter a restriction to ring member motion which is presented by the container pawl segments. The continued application of this force in a reverse direction will rupture the frangible bridge members and break away the closure member from the ring member thus leaving the separated ring member in an engaged position on the pawl portion of the bottle and visibly indicating that the closure has been removed.
Initial mounting of the closure body is accomplished by rotating the cap member until the closure body fully engages the container neck. The frangible bridge members should provide sufficient strength for maintaining mechanical integrity during this procedure while on the other hand enabling breaking of the cap when desired.
In order to facilitate initial mounting of the closure body on the container neck without rupturing the frangible members during this procedure, the closure body has generally been fabricated of a polymer plastic such as polyethylene which exhibits a resilient characteristic and permits the closure ring member to experience a limited deflection as the ring ratchet segments stretch and slide over the container pawl segments. However, a relatively large number of frangible members have also been provided to assure the desired mechanical integrity of the closure body during the initial mounting procedure. At times up to nine frangible members have been provided. As the number and holding capacity of these members is increased, the breakaway force is disadvantageously increased and often presents an imposing task to the housewife and to young children.
Closure bodies of the type described utilizing a resilient polymer plastic are formed of materials which are generally fabricated by an injection molding technique. This process is a relatively more expensive fabrication process than a thermoforming process for fabricating polymer plastic articles. However, the latter process is generally limited to polymer plastics which do not exhibit resilient characteristics as have been utilized with closure bodies as described hereinbefore.
Other desirable characteristics in a tamper-proof closure body include severing the frangible bridge members with the ring member which is then discarded thus avoiding the potential for abrasion to the hand from the sheared bridge members should they be retained on the cap member. It is also desirable that the ring configuration avoid the accumulation of foreign particles which contributes to potential contamination in edible goods.